1. Field of the Invention
The present invention relates to a device that prevents thermal deformation of a glass substrate needed for an organic semiconductor device and more particularly, to a shadow mask frame having heat-radiating and cooling functions, and a chuck plate used in attaching a glass plate to a shadow mask and having a cooling means, in which a refrigerant is circulated in the chuck plate, thereby preventing the temperature from increasing in the glass plate due to radiant heat from a deposition source under a vacuum atmosphere or conductive heat caused by contact with a shadow mask, thereby improving precision of the alignment between the glass substrate and the shadow mask.
2. Discussion of Related Art
Generally, an organic thin film of an organic semiconductor device such as an organic light emitting diode, for example, is formed by evaporating a low molecular organic material under a vacuum atmosphere, or by using a spin coating method, a dip coating method, a doctor blade, or an inkjet printing method after dissolving a polymer organic material in a solvent.
In particular, where the thin film including the low molecular organic material is fabricated in the vacuum atmosphere, a shadow mask having a predetermined pattern is needed for depositing an organic material at a proper layer. The shadow mask is fixed to a shadow mask frame. When a glass substrate is provided it is aligned with and attached to the shadow mask, and then a film growth process is performed. During the film growth process, a dotted-type or linear-type organic material deposition source is used to deposit the low molecular organic material on the glass substrate according to a predetermined pattern.
FIG. 1 schematically illustrates a typical deposition process using a vertical type deposition source, which directs a low molecular organic material towards a mask having a predetermined pattern when an organic light emitting display is fabricated, for example. In the deposition process, a shadow mask 20 having a predetermined pattern is mounted to a shadow mask frame 10, and then a glass substrate 30 is aligned by a chuck plate 40 and a rubber magnet 50. Then, a deposition material from a vertical type deposition source 70 is deposited on the glass substrate 30 via the shadow mask 20. Here, the deposition process is performed in a vacuum atmosphere.
In the above described deposition process, radiant heat R is transferred from the deposition source to the shadow mask and, thus, increases its temperature. As the temperature of the shadow mask rises, it thermally expands and thereby decreases the precision of a pattern position of an organic light emitting diode. This reduces the precision of the pattern position for representing red R, green G and blue B colors and results in the mixing of R, G and B colors, whish is known as “discoloration defective.”
Further, the glass substrate is affected by not only the radiant heat from the deposition source but also conductive heat due to direct contact with the shadow mask, so that the temperature of the glass substrate continuously rises. Particularly, in the case of the glass substrate, it is difficult to radiate away the heat, which accumulates via successive deposition processes. Therefore, the difference in thermal deformation between the glass substrate and the shadow mask becomes larger when only the shadow mask frame is cooled.